Quick Answer
Best overall: the Kidde 10-Year Sealed Battery detector (~$40) gives you a digital CO readout and a decade of maintenance-free protection. For whole-home coverage on a budget, the First Alert CO400 6-pack (~$120) protects every level at once.
All prices are approximate and change often—check the current price at the link. Every detector below is UL 2034 listed.
Quick Comparison
| Detector | Price | Power | Best For |
|---|---|---|---|
| Kidde 10-Year Sealed | ~$40 | Sealed 10-yr battery | Best overall |
| First Alert CO400 (6-pack) | ~$120 | Replaceable battery | Whole-home value |
| First Alert CO410 | ~$35 | Battery + digital | Digital on a budget |
| Kidde Plug-In + Backup | ~$30 | Plug-in + battery | Outlets & hallways |
The Picks
1. Kidde 10-Year Sealed Battery — Best Overall
Digital display, zero maintenance for a decade
~$40
Buy on AmazonThe sealed lithium battery lasts the full life of the alarm, so there are no battery changes and no midnight low-battery chirps. A digital display shows the actual CO level in ppm and remembers the peak reading—useful for spotting a slow leak before it becomes dangerous. Replace the whole unit at 10 years. For most homeowners this is the easiest reliable choice.
2. First Alert CO400 (6-Pack) — Best Whole-Home Value
Cover every level and bedroom at once
~$120
Buy on AmazonBuying a multipack is the cheapest way to protect an entire house—the CDC and fire departments recommend a CO alarm on every level and near every sleeping area, and a 6-pack covers a typical two-story home with spares. These are simple, dependable battery units; just note the battery is replaceable rather than sealed, so plan on periodic battery changes.
3. First Alert CO410 — Best Digital Readout for the Money
Battery-powered, shows CO in ppm, often on sale
A dependable battery-powered CO alarm with a digital display that shows the current level in parts per million plus peak-level memory—so you can catch a low, slow leak before it sets off a full alarm. It runs on replaceable batteries (cheaper up front than a sealed unit) and is frequently discounted, making it the best digital readout for the money. Replace the whole alarm at the end of its sensor life (about 7 years).
4. Kidde Plug-In with Battery Backup — Best for Outlets
Constant power, keeps working in an outage
~$30
Buy on AmazonA plug-in unit runs on household power with a battery backup that keeps it working during outages—convenient for hallways and finished basements with accessible outlets. Because a power outage can coincide with running a generator or alternate heat (a common CO risk), the battery backup here matters.
How to Choose a CO Detector
Sealed 10-year vs. replaceable battery
Sealed models cost slightly more but never need a battery change and won't chirp at 2 a.m. Since the CO sensor only lasts 7–10 years anyway, the sealed battery lasts about as long as the detector. Replaceable-battery units are cheaper up front and let you buy multipacks affordably.
Digital display
A display showing CO in parts per million (ppm), with peak-level memory, lets you spot a low-level leak before it triggers a full alarm. Worth the small premium, especially near furnaces and attached garages.
Standalone vs. combination smoke + CO
Combos save space and cover both hazards in one spot; standalone CO units are cheaper to replace and easier to place exactly where CO risk is highest. Just make sure your home has both smoke and CO coverage.
Placement matters as much as the model
Even the best detector fails if it's in the wrong spot. Put one on every level and near every bedroom, and follow the manufacturer's height guidance. See our CO detector placement guide for exact locations floor by floor.
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Frequently Asked Questions
What type of carbon monoxide detector is best: battery, plug-in, or hardwired?
For most homes, a battery-powered detector with a 10-year sealed battery is the simplest reliable choice—no wiring and no battery changes for a decade. Plug-in models with battery backup are good near outlets, and hardwired interconnected alarms (where one triggers all) are ideal for new construction or whole-home coverage. All three work; pick based on your wiring and how much maintenance you want.
Do I need a combination smoke and carbon monoxide detector?
A combination smoke + CO unit saves space and covers both hazards in one device, which is convenient near bedrooms. The trade-off is that when either sensor reaches end-of-life you replace the whole unit. Standalone CO detectors are cheaper to replace and let you place CO alarms exactly where they're needed. Either is fine as long as you have both smoke and CO coverage.
Are 10-year sealed-battery CO detectors worth it?
Yes, for most people. Sealed 10-year models cost a little more up front but eliminate battery changes and the 2 a.m. low-battery chirp for the life of the alarm. Since the CO sensor itself only lasts 7 to 10 years, the sealed battery lasts about as long as the detector—so you simply replace the whole unit when it expires.
How many carbon monoxide detectors do I need and where?
Install a CO detector on every level of your home and near every sleeping area so an alarm can wake you. Place them per the manufacturer's instructions, away from fuel-burning appliances and vents that can cause nuisance alarms. See our CO detector placement guide for exact locations on each floor.
How long do carbon monoxide detectors last?
Most CO detectors last 5 to 10 years—many are rated for 7 years, and sealed models for 10. The sensor degrades over time regardless of the battery. Check the manufacture date on the back and replace the unit when it nears its rated lifespan or starts an end-of-life chirp.